Community codes of conduct as proactive intervention for toxicity in games.

So called "toxic behaviors" (e.g., hate speech, harassment, doxxing) are pervasive in online gaming communities, with research consistently documenting significant negative consequences for player wellbeing, community health, and industry revenue. While gaming studios and platforms have developed a range of reactive and proactive moderation strategies to address these harms, most existing approaches remain reactive, focusing on punishment after harm has already occurred. Community codes of conduct represent a foundational yet underutilized proactive intervention that has received comparatively little systematic attention. This literature review synthesizes existing research to address two core questions: (1) What is known about the design, implementation, and accessibility of community codes of conduct in gaming environments? and (2) How do codes of conduct influence player behavior? Drawing on a final corpus of 84 articles identified through systematic search of academic databases and supplemented by transparency reports from major gaming studios, the review maps the current landscape of both reactive and proactive moderation approaches before examining the specific role of community governance documents. Findings reveal significant gaps between current industry practice and evidence-based best practice. More than half of popular multiplayer games either lack accessible codes of conduct or bury them within legal documentation, limiting meaningful player engagement. Where codes do reach players, however, the evidence is promising: well-designed codes are associated with measurable reductions in toxic behavior, increased community engagement, and stronger community norms. Design features that enhance effectiveness include prominent placement and readability, values-centered and game-specific content, community-centered participatory development, transparent enforcement mechanisms, and integration of peer and community social influence. Despite these positive indicators, the evidence base remains limited, with most studies examining discrete platforms and short-term outcomes. This review concludes with evidence-based recommendations for industry practice, synthesized into the EFFECT Framework - a practical tool distilling six core evidence-based design principles for developing community codes of conduct that actively shape community culture. Together, these contributions call for greater research investment in how codes of conduct can be optimized as living community tools (rather than static legal documents) to meaningfully reduce toxicity and build resilient gaming communities.